This invention relates to the conversion of coal into hydrocarbons, sometimes referred to as gasification or liquefaction of coal, and has particular relationship to such conversion by reactions involving principally coal and water. These reactions, in whatever way they are carried out, demand substantial quantities of energy; in addition some of the coal reacted may be dissipated in waste products. At the cost of this energy and the dissipated coal the remaining coal is converted into a more useful gaseous or liquid form.
The prior art relating to the conversion or gasification of coal is typified by the following processes:
HYGAS developed by the Institute of Gas Technology.
BI-GAS developed by Bituminous Coal Research.
The Lurgi process widely used in Australia, South Africa and Germany.
COED (Char Oil Energy Development) developed by FMC Corporation supported by the Office of Coal Research (See Document 2).
SYNTHANE developed by the Bureau of Mines.
Kellog developed by M. W. Kellog Co.
CO.sub.2 Acceptor developed by Consolidated Coal Company.
H-Coal, a liquefaction process, developed by Hydrocarbon Research Inc., funded by the Office of Coal Research.
Hydrodesulfurization, also liquefaction, developed by the Bureau of Mines.
COG (Coal-Oil-Gas Refinery), also liquefaction, investigated by Chem Systems Inc. and Pittsburgh & Midway Coal Mining Company.
Methanol, also liquefaction.
In these prior-art processes steam is mixed at one stage or another with the coal. The coal reacts with the steam, part of the coal is converted into a hydrocarbon, usually CH.sub.4, but a substantial part of the coal is converted into carbon dioxide which is exhausted into the atmosphere adding to the pollution problems. Typically, in the HYGAS process the most-active fraction of the coal is hydrogasified to form methane with the hydrogen derived from the volatile components of the coal and the less-active fraction is reacted with steam to produce additional hydrogen for the hydrogasification and carbon dioxide. Where coal is used to supply the energy for the processes there is a depletion of the coal in addition to the loss by dissipation. Prior-art conversion processes have then suffered from the disadvantage that their use of the coal has not been efficient.
It is an object of this invention to overcome the above-described disadvantage of the prior-art processes for converting coal into hydrocarbons and to provide a method for effecting such conversion in the use or practice of which the fraction of the coal converted into hydrocarbons shall be maximized and the fraction of the coal which is consumed without being converted or is dissipated, shall be minimized.